import solids; import animation; currentprojection=orthographic((0,5,2)); currentlight=(0,5,5); settings.thick=false; settings.render=0; int nbpts=200; real step=2*pi/nbpts; int angle=10; unitsize(1cm); triple[] P=new triple[nbpts]; for(int i=0; i < nbpts; ++i) { real t=-pi+i*step; P[i]=(3sin(t)*cos(2t),3sin(t)*sin(2t),3cos(t)); } transform3 t=rotate(angle,(0,0,0),(1,0.25,0.25)); revolution r=sphere(O,3); draw(surface(r),lightgrey); draw(r,backpen=linetype("8 8",8)); animation A; for(int phi=0; phi < 360; phi += angle) { bool[] front=new bool[nbpts]; save(); for(int i=0; i < nbpts; ++i) { P[i]=t*P[i]; front[i]=dot(P[i],currentprojection.camera) > 0; } draw(segment(P,front,operator ..),1mm+blue+extendcap); draw(segment(P,!front,operator ..),grey); A.add(); restore(); } A.movie(0,200);